The present invention relates to a suspension or axle system for a vehicle, such as a bus or truck, wherein the rear wheels are steerable. The rear wheel steering system is intended to be utilized with a vehicle having combined with a conventional front wheel steering system.
It is now well appreciated that a vehicle having steerable front and rear wheels provides the bus operator with many maneuvering advantages not available with a conventional front wheel steering vehicle. While combined front and rear wheel steering systems have advantages for any type of vehicle, such combination is particularly helpful with relatively long vehicles such as buses and trucks. Specifically, it is common that when such later vehicles turn a corner, they either have to make a very wide turn or, alternatively, in making a short turn the rear wheels of the vehicle are apt to either bump or ride over a curb. By having rear wheels that are steerable, the rear end of the vehicle may be kept away from a curb while the front end of the vehicle is making a relatively sharp turn.
It is not only an object of the present invention to provide a steerable rear wheel system, but also to combine such system with a suspension or dead axle system which provides exceptional lateral stability for the vehicle. The stability is achieved basically in two ways. First, the unique axle design allows the body supporting springs to be located outboard in general longitudinal alignment with the steerable wheels. Second, the associated differential drive mechanism is mounted directly to the vehicle body and coacts with the axle to enable the body to be supported closer to the ground to thereby enhance stability as well as enabling the vehicle body to be disposed lower to the ground which also enhances lateral stability.
The basic suspension or axle system with which applicant's invention is combined is shown in U.S. Pat. No. 4,343,375 VEHICLE DRIVE WHEEL SUSPENSION - Manning. The advantages of the Manning suspension as described in the aforementioned patent are also applicable to the present application and are incorporated herein by reference. The advantage of the earlier Manning system are to provide a suspension wherein the unsprung weight of the system is greatly reduced both by supporting the differential from the vehicle body rather than the axle as well as providing a dead axle system which may be made of a much lighter construction then conventionally forged axle systems.